The second blessing before kriyat Shema focuses on Torah study and observance. In the morning, we mention the Patriarchs to whom God "taught the laws of life", and then we ask that God "lead our hearts to understand, perceive, listen, learn, teach, guard, perform, and uphold all the words of this Torah". In the evening, we express our desire to "rejoice in the words of Your Torah and Your commandments forever, for they are our life and the length of our days, and we shall study them day and night." Virtually the entire blessing is on this topic, in both the morning and the evening.
The topic is a logical one. The Shema is one of the main sources for the mitzvah of Torah study; its reading is itself a performance of Torah study; and it is one of the most memorable passages on the topics of mitzvah observance and reward and punishment. Some sources suggest that this blessing functions as the usual blessing said before performance of a mitzvah (and therefore one should not speak between them and the Shema) - in which case they certainly must be on the same topic as the Shema.
But there is one main deviation from this topic - at the beginning and end of each blessing. There, rather than Torah study, the topic is love. The blessing starts by mentioning the "great love" or "eternal love" God has shown us, and ends by blessing God who "chooses Israel in love", or "loves His people Israel". Why mention love here?
I think the answer lies in the second line of the Shema. "You shall love Hashem your God, with all your heart, with all your soul, and with all your might." The first line of the Shema is a basic declaration of loyalty to God. Once that is accomplished, we list the things we must do for God - and the first of those to love.
The remaining things, of course, are all about Torah study - keeping the Torah in mind, reciting it, teaching it, speaking of it, placing reminders of it on our body and houses. The overall structure closely echoes the blessing recited before the Shema - there, too, the introduction is about love, and the body of the paragraph is about Torah study.
Of course, rather than the Shema echoing the blessing, it is the blessing which echoes the Shema, since the blessing was composed to accompany the Shema rather than vice versa.
There is one difference though. The blessing talks Torah study plus about God's love for Israel. The Shema talks about Torah study plus Israel's love for God. Each contains love, but the direction of the love is reversed.
Here is one possible explanation of this difference. Tanach repeatedly likens the relationship between God and Israel to that between a husband and wife. Just as a successful marriage must involve mutual expression of love and commitment from both sides, so must God's relationship/covenant with the Jewish people. God showed us love in giving us the Torah; we show love by keeping it. In the Shema (which is God's words) He provides us with commandments through which we can merit reward and closeness to God; in the blessing (which is our words) we thank God for these commandments and express our wish that nothing ever prevent us from keeping them. Each party in the relationship mentions the love the other party shows them, and through this, the relationship between them is mutually strengthened.